Octane analyzer

ABSTRACT

MEANS TO DETERMINE A CHARACTERISTIC OF A HYDROCARBON, SUCH AS THE OCTANE RATING OF GASOLINE, BY REACTING A SAMPLE OFTHE HYDROCARBON WITH AN OXYGEN CONTAINING GAS, SUCH AS AIR, UNDER CERTAIN CONDITIONS TO MAINTAIN A MILD REACTION LESS VIRGOROUS THAN AN EXPLOSION. THE TIME ELASPED BETWEEN INJECTION OF THE HYDROCARBON INTO THE GAS STREAM AND REACTION OF THE HYDROCARBON INTO THE GAS STREAM GAS, AND/OR SOME FACET OF THE SEVERITY OF THEREACTION, ARE CORRELATABLE TO THE VALUE OF THE CHARACTERISTIC OF INTEREST OF THAT HYDROCARBON.

June 12, 19%

R. M. CLINTON ET AL {73 19 mm ANALYZER "Filed Aug. 31, 1971 SEVE/P/T)77/145 28 2/ I f 1 f 1 PL M 2: E MO0E1\ [L J 58 23 H" I sEl fRlry f MODEN 64 DIFFERENT/Arm RDER 7 (QJQL AT/ME 56 26 SAMPLE m/ [/2 f 48 OVENSAMPLE Y PROGRAMMER [MEN/0N R 24 I/E/VT a ORA/N United States Patent 01fice 3,738,810 OCTANE ANALYZER Russell M. Clinton III, Gibsouia, andThomas J. Puzniak,

Cheswick, Pa., assignors to Gulf Research & Development Company,Pittsburgh, Pa.

Filed Aug. 31, 1971, Ser. No. 176,593 Int. Cl. G011 23/22; Gtlln 33/22US. Cl. 23-230 PC 27 Claims ABSTRACT OF THE DISCLOSURE This inventionpertains to the analysis of hydrocarbons, and in particular it pertainsto such analysis by means of mildly chemically reacting individualsamples of such substances with an oxygen containing gas so as tomaintain reaction conditions less violent than an explosion. Theinvention comprises the use of a mild oxidation reaction which emits noapparent light and which appears to be homogenous in time and space,thus apparently not having a flame front. Therefore, such a reaction maybe thought of as less vigorous than a combustion, and hence the Wordcombustion as used in the specification and claims herein shall beunderstood to mean reactions at and more vigorous than a reaction at thenon-inclusive upper limit of the mild oxidation reactions used in theinvention. The invention comprises correlating one or more parameters ofthis mild reaction to some characteristic of the hydrocarbon sample.Specifically, when measuring octane rating, correlations have been foundto pressure pulse produced, temperature pulse produced, rate of reactionor slope of the temperature or pressure curve, and elapsed time betweensample injection and the beginning of the reaction. The first threeitems above, pressure, temperature, and rate of reaction, may be thoughtof together as the severity of the reac tion. Further, as will appearbelow, it may be desirable to handle combinations of these parameters topossibly make an additional analysis of the sample. The correlation, ofwhichever type or combination, can be performed with the use ofcalibration curves, or by direct comparisons with similar type resultsobtained from similar standardized substances having known values of thecharacteristic of interest, or in other ways which may suggestthemselves to those skilled in the art.

It is an object of the invention to provide method and apparatus of thecharacter described particularly adapted to determine the octane ratingof gasoline. In the following description the invention is described interms of an octane monitor for gasoline. It is anticipated that octanerating determination of gasoline will be the most important use of theinvention, however, it is thought that the invention may be operable todetermine other characteristics of other hydrocarbon substances. Forexample, the invention could possibly be used in determining the cetanerating of diesel fuel, or with other refinery processes, in blendingoperations, or the like, involving a hydrocarbon substance.

Heretofore, there was not a completely satisfactory method of measuringthe octane rating of gasoline. It is tremendously important to therefiner to accurately know 3,738,810 Patented June 12, 1973 the octanerating of his gasoline. In order to assure minimum ratings, and toaccommodate inaccuracies in existing techniques, the refiner usuallyblended the final gasoline so that its octane rating exceeded theminimum specification. This practice costs refiners a great deal ofmoney. For example, as an indication of orders of magnitude only, thisexcess octane rating can cost as much as $0.25 per barrel of blendedgasoline.

There are presently available two basic types or general classes ofmethods of measuring octane rating. The first and more basic method is,generally, to burn the gasoline in a special engine, and to then detectthe sound of knocking. This system is very slow, expensive in that itrequires a skilled operator, not readily adaptable to on-streamoperation, requires frequent and expensive maintenance, experiencesdifiiculty in holding engine conditions constant between the tests dueto drifting of the engine, and is subject to the objection that soundper se is a diflicult characteristic to handle scientifically. However,the industry accepted standard is an engine method, and the standardizedfuels used in the method of the invention and in the second generalclass of analytical techniques, are standardized by this acceptedsystem. Still within this first class of octane determination methodsand apparatuses are those devices which built up from an engine byautomating it, in various ways, thus removing or diminishing thedisadvantage of having to have an operator present. However, most of theother disadvantages of the basic engine method still apply to automatedengines, perhaps the most important one of which is the difficulty ofon-stream application.

The second broad class of octane determination techniques do not use anengine, but rather operate on the gasoline itself in various differentmanners. The present invention is of this general class. At present, themost popular such technique reacts gasoline with air in a specific typeof chamber under controlled and variable flow, temperature, and pressureconditions so as to pro duce a cool flame in the chamber. A cool flameis a chemical reaction less violent than an explosion, but more violentthan the mild reactions used in the present invention, and ischaracterized by the production of a characteristic luminosity, i.e., acertain kind of light production, and therefore may be considered acombustion. The principle of operation is to detect this light or theheat accompanying it, and to then adjust flow rate, pressure, and/ortemperature to physically hold the area of luminosity or cool flame at aconstant location within the chamber. The amount of adjustment of thesecontrol inffuences needed to hold the cool flame steady, in response tocompositional changes in the gasoline being analyzed which reflect asfactors tending to move the cool flame region in the chamber, iscorrelated to the octane rating or changes in the octane rating of theubstance under analysis.

These cool flame based systems suffer from many problems. First, a coolflame is inherently an unstable phenomenon. Thus, operation of suchmethods and apparatus is at all times critical and extremely sensitive.The apparatus itself must be vertically oriented so as to eliminate anygravity effects on the cool flame region which has a different densitythan the remainder of the substances in the reactor. Anotherdisadvantage of cool flame based techniques is that they are one stepfurther removed from the reaction than is the present invention. Thatis, in the present invention the time for the sample to react and/or theseverity of the reaction is correlated to the final characteristic ofinterest. In these prior methods it is some outside influence, which hassome effect on the reaction, which is correlated to the finalcharacteristic of interest. Thus, the advantages of the presentinvention over the prior art of itsgeneral type include that it providesmethods and apparatus which operate in a broad reaction region asopposed to the narrow and unstable cool flame region and is thereforenot highly critical in operation, easier to use, and more forgiving ofminor errors. The reactor used in the present invention is insensitiveto and uneffected by orientation. The method of the invention is closelyand directly related to the chemical reaction which occurs.

The underlying basis of the present invention is the discovery that whena gasoline or other hydrocarbon is mildly reacted with an oxygencontaining gas under certain conditions selected to keep the reactionless vigorous than either an explosion or a cool flame, the time elapsedbetween injection of the hydrocarbon into the gas stream and reaction ofthe hydrocarbon with the oxygen in the gas, and/or the severity of thereaction, is directly correlatable to the octane rating of thatgasoline, or to some other characteristic of interest of some otherhydrocarbon. The apparatus embodying the invention includes a pen andchart type recorder for charting or trending reaction times and/orseverity. Initial testing of the invention, in the severity mode, hasshown that different gasolines produce characteristically shaped outputcurves, and that therefore the invention may be useful as both aqualitatively and quantitatively analytical device.

The quality of a gasoline is determined by a large number of factorswhich affect the performance of that gasoline in an engine. However, theword quality" as used in the specification and claims herein shall beunderstood to refer primarily to the mix of particular types ofcompounds in that gasoline, as is known to those skilled in the art. Forexample, a reformate is high in aromatics, other quality gasolines suchas alkylates may contain varying quantities of branch chain paraffins,and the like. Tests of the capabilities of the invention have shown thatoctane rating correlated to both elapsed time between sample injectionand the start of the reaction, and to some one or some combination ofthe various facets of the severity of the reaction. Tests with thepressure pulse produced by the reaction have not been run, but it isexcepted that these results will parallel the temperature rise resultsbecause both are indicative of reaction severity, and also because theresults of the correlation to slope of the reaction curve paralleled thetemperature results. Thus, the term severity shall refer to temperaturerise and/or pressure pulse, and/or slope of the reaction curve, andshall be understood to have that meaning in the specification and claimsherein. This testing has also shown that the severity correlations aremore sensitive to octane rating than the elapsed injection timecorrelation, but that severity is also more sensitive to quality of thesample. Thus, when an unknown quality sample is being analyzed, theelapsed time octane correlation would be preferred since it is not assensitive to quality. Conversely, where known quality samples are beinganalyzed, then some severity correlation would be preferred because thesensitivity to octane is better and the increased sensitivity to qualityis not disruptive because quality is either constant or else, since itis known, can be accommodated in the data handling.

The apparatus of the invention permits both kinds of correlations, i.e.,elapsed time or at least one of the various kinds of severity, with onlythe movement of a switch. An interesting future capability of theinvention would be to run both severity and elapsed time types ofanalyses, and to then use statistical methods and a computer to analyzethe relatively large amount of data generated to determine both thequality of and the octane of the unknown sample. This sort of additionaldetermination may be made possible by the different sensitivities of thevarious correlations as mentioned above, combined with suitablemathematical analytical techniques.

-While air has been used in testing the invention, and it is anticipatedthat air will be used generally because of its easy availability,generally adequate service with the invention, and low price, it is ofcourse within the scope of the invention to use any other oxygencontaining gas. In any case, the amount of oxygen in the gas will be aknown percent of the gas. It is presently thought that there is someoptimum oxygen percentage for maximum accuracy, probably less than theamount of oxygen in ordinary air, but this facet of the invention hasnot yet been fully researched.

Thus, there is provided method and apparatus of the character describedwhich is simple in use and concept, economical, and includes no movingparts inherent to the analysis performed.

The above and other advantages of the invention will be pointed out orwill become evident in the following detailed description and claims,and in the accompanying drawing also forming a part of the disclosure,in which the sole figure is a schematic diagram of an apparatus whichhas been built in successfully testing the invention.

Referring now in detail to the drawing, 10 generally designatesapparatus which embodies the invention and comprises an oven 12 in whichis positioned a reactor 14 having an atmospheric vent 16 which extendsthrough the Wall of the oven and is suitably sealed therein. Means notshown will be provided to very accurately control the temperature of theoven 12 and hence of the reactor 14. Preferably, a high qualityproportional type of precision temperature controller will be used. Air,products of combustion, water, and the like exit from the reactor viavent 16. Further, the vent 16 serves to provide atmospheric pressure inthe reactor 14. For safety purposes, a flash back arrestor, not shown,is provided in vent 16.

The reactor 14 is preferably made of glass, preferably, Pyrex. In theexperiment work which has been done, it was found that a metal reactor,grade 316 stainless steel was tried, may interfere with the reaction,perhaps by having a catalytic effect on the reaction. However, furtherwork will be done in this area since a metal vessel is preferred simplybecause it would be more durable than glass, which durability isdesirable in an industrial environment.

The single preferred reaction temperature, for gasoline, isapproximately 315 C., with an operative range of 275 C. to 350 C., and apreferred range of 300 C. to 320 C. Tests have shown that above 350 C.the reaction becomes unstable, and it probably enters the combustion oreven the explosion zone. At temperatures less than 275 C. the reactionis not sufficiently vigorous to yield meaningful results, or else doesnot occur at all. Of course, different temperatures and ranges will beneeded for different hydrocarbons. The reaction is carried out at ornear atmospheric pressure via the vented reactor.

Means are provided to sense the temperature increase in the reactor asit occurs when the gasoline and oxygen react therein. To this end, amicro-thermocouple 18 is connected by a line 20 to a two position modeselector switch '19, and a second thermocouple 24 is connected by a line26 to said switch; a recorder 22 is connected by a pair of lines 21 and23 to the common terminals on switch 19. Because the reaction occursquickly, it is preferred that thermocouple 24 be as small as possible,and be located centrally within the reactor 14. It is thought that amicro-iron/constantan thermocouple would be best used at 24. The twothermocouples are connected into the recorder 22, when the selectorswitch '19 is so positioned, in a differential or so-called buckingmode, which results inno output on the recorder until there is somereaction, which reactions produce an output, such as the set of spikes28 shown in the drawing. The curves 28 represent the elapsed time modeof operation of the invention. The length of each of the lines 28 isproportional to the elapsed time between injection of the sample and thebeginning of the reaction. The chart paper would be travelinghorizontally in the dIaWing. How the spikes 28 and the second set ofcurves 30 representing the severity mode are produced will be explainedfurther below. The signals on the lines 21 and 23 may also be connectedinto a read-out device, not shown, which would automatically changeelapsed time between injection and reaction into octane number. Such adevice, in effect, would comprise a wired version of the calibrationcurve, could be used with or without recorder 22, is a simple matter forone skilled in the art to fabricate, and is optional. Further, as willbe clear to those skilled in the art, an output device other than or inaddition to recorder 22, such as a CR tube display, could be used. I

Means are provided to supply air or other oxygen containing gas to reactwith the gasoline supplied to the reactor 14. A conduit 32 supplies thegas to supply means 34 from any conventional source, such as a tank,bottle, or the service air readily available in industry. The supplymeans 34 includes several standard components, such as a throttlingdevice if needed, a flow controller or needle valve to control thequantity, and a rotometer to measure flow, all arranged in the usualmanner. Thus, the air supply means 34 provide a constant mass flow ofair or other oxygen containing gas for combustion, which constant flowis required in order to keep the reaction constant.

A conduit 36 delivers the gas from supply means 34 to a preheater coil38 located within the precision oven 12. After preheater coil 38 the gassupply system comprises a loop conduit 40 which provides an access point42 for sample injection. After injection point 42 a conduit 44 deliversthe sample laden air or gas through the wall of the oven and through thewall of the reactor and into the middle of the reactor, suitable sealingmeans, not shown, being provided where conduits pass through walls. Thegas and sample do not react in conduit 44 for several reasons. Theconduit 44 is small with respect to the relatively large reactor 14.Further, the conduit 44 is preferably smaller than the other conduits36- and 40, all to the end that a relatively high flow rate and thus ashort residence time of the gasoline and oxygen containing gas in theconduit 44 is achieved. In the constructed embodiment used insuccessfully testing the invention, conduit 44 was approximately 3inches in length, and the flow rate was such that residence time wasless than &0 Of a second. Since the quickest reaction tested required await for an elapsed time of about two seconds, and ranged up to orseconds for other gasolines, it appears certain that the gasoline justbarely has time to vaporize in passing through conduit 44, and that noreaction occurs therein.

Injection point 42 could be part of an automatic injection valve orother such means tapped into some flowing stream which is to beperiodically sampled, whereby the invention can be used in an on-streamapplication. Such arrangements and the sampling components required arewell known to those skilled in the art. In a laboratory version,injection means 42 could comprise simply a rubber septum at the end ofconduit 44.

Means are provided to determine the time at which the sample is injectedinto conduit 44 and the reactor '14, and to measure the elapsed timebetween the moment of injection and the time when the reaction occurs asde tertnined by the differential thermocouples 18 and 24. It is thiselapsed time upon which the invention depends for one of itscorrelations to octane number. Because this elapsed time dilfers fordifferent substances, it can be seen that it is a parameter of thesample.

Block 46 represents means to control sample injection. In a laboratoryversion using a syringe and septum type of arrangement, block 46 couldrepresent a solenoid to automatically operate the syringe, or thesyringe itself where the system is operated manually. In an onstreamapplication, block 46 would represent the control portion of theautomatic sampling valve. In any case, sample injection occurs under thecontrol of' a programmer 48 which provides a signal on a line 50 toinjection control means 46, which in turn controls the physicalinjection of sample, which physical injection is represented by thearrow 52 on the drawing. A pair of lines 54 and 56 interconnectprogrammer 48 with timing means 58. A pair of lines 60 and 62interconnect circuit 58 to the second position of the selector switch19. A line 64 interconnects timing means 58 with a ditferentiatorcircuit 66-. Dilferentiator 66 receives signals from the twothermocouples 18 and 24 via branching lines off of the thermocouplelines 20 and 26. Programmer 48 may comprise a motor driven multi-cam andswitch array type of device, or any other suitable programming means.Timing means 58 may comprise an RC circuit, a digital timer, or thelike. The function of these components will be described as thisspecification continues.

With regard to amount of sample hydrocarbon substance, it is desired touse the smallest quantity which will yield good results. Theelectronics, especially the thermocouples, are a source of electronicnoise, and the amount of hydrocarbon substance reacted must be large'enough to overcome this instrument noise. In tests run to prove theinvention, samples in the range of about 25 to about 50 microliters wereused. Another advantage of using small samples is that they reactquickly, clean-up quickly with just the normal flow of air or oxygencontaining gas, and thereby permit running successive samples rapidly.Overly large samples produced sufiicient heat to upset the thermalbalance of the apparatus. Going to extremes, an excessively largesample, with respect to the size of the reactor, could cause anexplosion.

Tests of the invention have shown a reproducibility of within less thanhalf an octane number, which is greater than the accuracy of more thanhalf an octane number which is obtainable by engine methods. Thus, theinvention octane determination methods and apparatus have a greaterreproducibility than the standard against which they are calibrated. Inuse, the calibration curve has been found to be substantially a straightline with a slope equal to about /2 of a second per octane number. Thecalibration curve is obtained by repeatedly running samples of knownoctane rating through the invention apparatus. It is thought that theelapsed time for reaction to initiate is greater with higher octanefuels because such fuels produce a low temperature oxidation lessreadily.

An important operating condition in all modes is that a relatively smallsample be reacted with a relatively large quantity of air in arelatively large volume. As an example of these conditions, in testswhich were run to test the invention, elapsed time mode, about 25microliters of unleaded gasoline were injected into a flowing air streammoving at about 300 cm. per minute into a glass reactor having a volumeof about 500 cm. The oven was accurately held at a temperature of 315 C.For this particular gasoline which had a known octane number of 92,

e elapsed time was 11.8 seconds. A similar gasoline but of 88 octanerequired an elapsed time of 9.8 seconds when tested under the sameconditions. Similar results were obtained with the inventions severitymode of operation. Generally, the higher the octane the less severe thereaction.

When switch 19 is in the upper position or time mode, then thecomponents 58 and 66 come into play. Ideally, in this mode, theapparatus should measure the elapsed time between the moment ofinjection and the beginning of the mild oxidation reaction of the samplegasoline. It is a simple matter to locate the moment of injection intime, but it is more difficult to fix the beginning of the reaction. Thedifferentiator circuit 66 can be used to measure the time rate ofchange, analogous to acceleration, of the temperature to thereby detectand trigger other components upon the first positive indication that thereaction has initiated. Alternatively, a recorder could be in block 66,and some arbitrary amount of pen motion used to activate a switch, inlieu of a differentiator circuit, to thereby fix a time [for thebeginning of the reaction. The timing means 58 serves to convert theactual elapsed time into an analog signal for driving the recorder 22and may comprise a digital timer or simply an ordinary tunedresistance/capacitance circuit, with the charge on the capacitor beingproportional to the elapsed time. The two lines 54 and 56 betweencomponents 48 and 58 serve to start the timing means and to reset thetiming means. The two lines 60 and 62 are needed for plus and minus orground millivolt output to drive recorder 22. The sequence of events is(1) programmer 48 via line 50 operates means 46 to cause a sample to beinjected and simultaneously starts timing means 58. (2) Device 66 vialine 64 stops timer 58 at the start of the reaction. (3) The programmer48 sends a signal to the timer 58 to cause the stored signalproportional to elapsed time to be recorded on recorder 22. (4) Theprogrammer resets the timing means.

The set of curves 28 on the drawing are the time spikes produced by aseries of reactions, their heights being proportional to each elapsedtime. As mentioned above, this elapsed time mode of operation of theinvention is less sensitive to octane rating than the severity mode, buthas the advantage that it is also less sensitive to varying quality inthe sample. Thus, the heights of the lines 28 correlate to octanerating, and so correlate substantially irregardless of sample quality.

When switch 19 is moved, either manually or with suitable automaticmeans, to the lower or severity mode, then the recorder 22 or otherdisplay means is driven directly by the thermocouples 18 and 24 toproduce curves such as 30. In this case, the height of each curve abovethe base line correlates to octane rating of the sample. Also, we havefound that the slope of the reaction curve correlates to octane rating,and, as defined above, this slope is included in severity. Further, wehave found that the shape of each of the curves 30 can be helpful inidentifying an unknown or an unknown quality of a sample. That is,certain qualities produce characteristically shaped curves. Since theseverity modes of the invention are more sensitive to both octane andquality, it is not preferred when analyzing a sample of unknown quality.A possible (future capability of the invention, however, is to combinethe respective strengths of the various modes of operation of theinvention in order to permit determination of both octane rating andquality of an unknown sample.

The drawing is a schematic of a laboratory or breadboard embodiment ofthe invention, but it does prove the principle and does operate. As iswell known, a great deal of polishing and refinement could and would bedone in building an industrial or commercial quality apparatus. Asexamples of such improvements, the operative parts of the inventionincluding reactor 14, the ovens operative parts, and the thermocouples,may all be housed in an efiicient temperature shield such as a dewarflask, and then the entire apparatus, except for the display and thecontrols, placed in an explosion proof housing. Further refinementsmight include the ability to analyze several streams at the same time,computer read-out, or a tie-in to an automatic blending operation. Anincreased chart speed in recorder 22 would be needed (for the slope ofthe reaction curve type of severity correlation.

While the invention has been described in detail above, it is to beunderstood that this detailed description is by way of example only, andthe protection granted is to be limited only within the spirit of theinvention and the scope of the following claims.

We claim:

1. A method of determining the value of a selected characteristic of ahydrocarbon substance, comprising the steps of injecting an individualsample of a predetermined amount of the hydrocarbon substance into astream of an oxygen-containing gas, whereby the sample is carried into areactor, mildly reacting the sample with the oxygencontaining gas atselected conditions in said reactor to keep the kinetics of the reactionslower than that associated with an explosion; detecting either thereaction parameter of the elapsed time between the injection of saidsample and the beginning of said reaction, or a reaction parameter ofthe severity of said mild reaction; and correlating a value for saidhydrocarbon substance characteristic to said detected parameterresultant of said mild reaction.

2. The method of claim 1, wherein the temperature rise produced by saidmild reaction is correlated to said selected characteristic of saidhydrocarbon substance.

3. The method of claim 1, wherein the slope of the reaction curveproduced by said mild reaction is correlated to said selectedcharacteristic of said hydrocarbon substance 4. The method of claim 1,wherein said correlation is made to both the elapsed time between theinjection of said hydrocarbon substance into said gas stream and thebeginning of said mild reaction, and at least one of the temperaturerise and the slope of reaction curve produced by said mild reaction.

5. The method of claim 1, wherein said hydrocarbon substance is gasolineand said selected characteristic is octane rating.

6. The method of claim 1, wherein said sample comprises a relativelysmall quantity of said hydrocarbon substance and said stream comprises arelatively large quantity of said oxygen containing gas, wherebysuccessive samples may be rapidly analyzed in said reactor.

7. The method of claim 1, wherein said oxygen containing gas comprisesair, and wherein the air is supplied at a constant flow per unit time.

8. The method of claim 1, wherein said reaction is carried out at aboutatmospheric pressure.

9. The method of claim 1, wherein said reaction is carried out at atemperature ranging from about 275 C. to about 350 C.

10. The method of claim 1, and the step of pre-heating said oxygencontaining gas before said step of injecting hydrocarbon substance.

11. The method of claim 1, wherein said reactor is housed within anoven, and wherein said step of detecting the beginning of the reactionis accomplished by the steps of constantly measuring the temperaturewithin the oven and continuously measuring the temperature within saidreactor, and diiferentiating the temperature rise in said reactor withrespect to time.

12. The method of claim 1, wherein the quantity of said sample isselected from the range of about 25 to about 50 microliters.

13. The method of claim 1, wherein said reaction is carried out at apreferred temperature ranging from about 300 C. to about 320 C.

14. The method of claim 13, wherein said reaction is carried out atabout 315 C.

15. In combination, a reactor, means for holding said reactor at aselected predetermined temperature, means for flowing anoxygen-containing gas through said reactor, means for injecting a sampleof a hydrocarbon substance into said flowing gas stream whereby saidsample is carried into said reactor, said injecting means comprising ahypodermic syringe and a rubber septum in a conduit carrying said gasstream or an automatic sample injection valve, whereby a continuouslyflowing stream of said hydrocarbon substance may be periodically andregularly sampled, means for detecting the reaction of said hydrocarbonsubstance with said oxygen-containing gas in said reactor, saiddetecting means comprising at least a part thereof located within saidreactor whereby said at least a part of said detecting means is directlyexposed to said reaction in said reactor, and means for correlating thevalue of either the reaction parameter of the elapsed time between theinjection of said sample and the beginning of said mild reaction or thereaction parameter of the severity of said mild reaction to a value of aselected characteristic of said hydrocarbon substance.

16. The combination of claim 15, said detecting means comprising meansfor measuring the time elapsed between the injection of said hydrocarbonsubstance and the occurrence of said reaction.

17. The combination of claim 15, wherein the oxygen containing gascomprises air, and means to supply a constant mass of air per unit time.

'18. The combination of claim 15, and vent means in said reactor,whereby said reaction is carried out at about atmospheric pressure.

19. The combination of claim 15, wherein said hydrocarbon substance isgasoline and said selected characteristic is octane rating.

20. The combination of claim 15, and means for preheating said gasstream before said stream encounters said injecting means.

21. The combination of claim 15, said temperature holding meanscomprising an oven in which said reactor is housed, said reactiondetecting means comprising a differential thermocouple array, saidthermocouple array comprising one thermocouple in said oven and said atleast a part of said detecting means located within said reactorcomprising a second thermocouple of said thermocouple array.

22. The combination of claim 15, said means for correlating at least oneparameter including a selector switch for selectively connecting saidreaction detecting means to display means in one of two manners:

(1) directly, or

(2) via means for detecting the beginning of said reaction.

23. The combination of claim 22, said display means comprising a pen andchart type recorder.

24. The combination of claim 22, said temperature holding meanscomprising an oven in which said reactor is housed, said reactiondetecting means comprising a differential thermocouple array, saidthermocouple array comprising one thermocouple in said oven, and said atleast a part of said detecting means located within said reactorcomprising a second thermocouple of said thermocouple array.

25. The combination of claim 22, said means for detecting the beginningof said reaction comprising a temperature to time differentiatorcircuit.

26. The combination of claim 25, said display means comprising a pen andchart type recorder, and an RC timing circuit for converting elapsedtime between injection and the beginning of said reaction into an analogsignal for driving said recorder.

27. The combination of claim 25, said display means comprising a pen andchart type recorder, and a digital timer for converting elapsed timebetween injection and the beginning of said reaction into a signal fordriving said recorder.

References Cited UNITED STATES PATENTS 3,527,567 9/1970 Philyaw 23230 PC3,533,745 10/1970 Fenske 23-253 PC MORRIS O. WOLK, Primary Examiner S.MARANTZ, Assistant Examiner US. Cl. X.R. 23253 PC; 7335

